1.1
=> 1.1 # in reality this probably doesn't equal exactly 1.1 deep down--but it's equal to 1.1's default so ruby 1.9.2 will display it as 1.1
0.9
=> 0.9
1.1-0.9
=> 0.20000000000000007 # now ruby 1.9.2 notices that "this 0.2 is not the same as the default float for 0.2" so it displays its full version to remind us of this fact.